1. Field of the Present Invention
The present invention relates to a noise preventing structure of a roller chain for suppressing a noise generated upon engagement of a roller chain with a sprocket or when a roller chain slides on a chain guide.
2. Description of Related Art
Heretofore, various proposals have been made for suppressing a noise generated upon engagement of a roller chain with a sprocket. For example, reference is here made to Japanese Patent Laid Open No. 17250/83, in which a hole is formed in the toothed bottom of a sprocket, a cylindrical member formed of urethane rubber is fixed into the hole, and a prismatic member also formed of urethane rubber is inserted inside the cylindrical member so that an end portion of the prismatic member projects from the toothed bottom of the sprocket. It is intended to suppress an impulsive sound by abutment of a roller with the end portion of the prismatic member.
In Japanese Utility Model Laid Open No. 126659/88, a noise suppressing structure is proposed in which an intermediate layer of an elastic material is sandwiched in between a pair of metallic plates having the same shape of teeth on the respective outer peripheral surfaces, to constitute a sprocket. The intermediate layer is partially projected from the toothed surface to form a buffer portion. A collision sound, resulting from collision of a roller with the sprocket toothed surface upon engagement of a chain with the sprocket, is suppressed by the buffer portion projecting from the toothed surface.
Further, a noise suppressing structure has been proposed in which a circumferential slot, deeper than the toothed bottom of a sprocket, is formed centrally of the width of the teeth of the sprocket toothed surface, and an elastic ring is fitted in the slot. The elastic ring has soundproofing teeth implanted therein. The soundproofing teeth are formed of a synthetic resin and project somewhat beyond the sprocket toothed top, to buffer the collision between a roller and the sprocket toothed surface upon engagement of a chain with the sprocket, thereby suppressing the resulting noise.
However, in all of the conventional noise suppressing structures referred to above, a noise generated by collision of a roller with the sprocket toothed surface or toothed bottom upon chain-sprocket engagement is intended to be suppressed, with no measures being taken against a rubbing sound generated between the inside surfaces of inner plates of the chain and both end faces of the roller.
More particularly, when the chain engages the sprocket, the roller comes into abutment against the toothed surface of the sprocket and thereby rotates, so that the inner plates and the end faces of the rotating roller rub against each other, thus generating a rubbing sound. This rubbing sound is generated not only upon chain-sprocket engagement, but also when the chain moves while being guided by a chain guide. Thus, it has so far been impossible to completely prevent the generation of noise in a chain drive.